The welding of the stringer or root weld or pass in pipeline welding is a difficult problem. When the stringer or root weld is made from the exterior of the pipe, it is difficult to achieve a sufficiently smooth weld surface at the interior of the pipe, and grinding or other finishing operations at the pipe interior are frequently required. The adjacent pipe ends must be accurately faced and accurately spaced to provide a uniform welding gap between the pipe ends. Often, obtaining adequate penetration through the root weld section is difficult, resulting in weakened welds which will not pass inspection.
Apparatus has heretofore been devised for welding of the stringer or root pass from the interior of the pipe. Such apparatus has been of limited proficiency because of the limited space available between the clamps which are necessary for clamping the pipe ends together for welding. The apparatuses which have been provided have been limited as to the amount of welding electrode wire which may be carried, so that frequent replenishing of the welding electrode wire has been required. Of special importance is the fact that such internal welding apparatus has required that the welding gap be lined up exactly perpendicular to the pipe axis, in order that weld skips will not occur around the periphery of the welding gap caused by failure of the weld to bridge the gap.
Examples of the apparatuses which have been provided in the art are shown in U.S. Pat. Nos. 3,461,264 and 3,551,636.
The present invention seeks to provide an improved pipe clamp apparatus including provision for internal welding of the stringer or root pass in pipeline welding, which will be entirely satisfactory and which will not require the precise lining up of the internal welding apparatus with the welding gap or crack, and which will not require precise alignment of the adjacent pipe ends.